Hello,
For what you describe Thunderbird really does sound like the best fit.
If command line arguments are all that you lack, then perhaps check out these couple of pages and see if that helps you to set-up the command line options you want:
http://kb.mozillazine.org/Commandline_arguments%28Thunderbird%29
http://www.mozilla.org/docs/command-line-args.html
http://kb.mozillazine.org/Commandlinearguments
Now, keep in-mind that Thunderbird is just a re-branded / slightly refined version of Mozilla's standard e-mail / news-reader program. So, the Mozilla arguments should work fine with Thunderbird.
But, if you are uncomfortable experimenting with the Thunderbird version, you could go and get the Mozilla version which would be basically the same as Thunderbird (just not with the Thunderbird name).
I hope this helps.
Let us know if you have other questions.
P.S., if you'd like, go ahead and click the "Helpful" or "Solved" buttons on any of the posts / replies above if you feel they were helpful or adequately answered your question.